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Software improves accuracy of GPS

US: Researchers at the Ohio State University in the US developed a software to fix GPS errors. According to the initial test, the software enabled centimetre-scale GPS positioning – including altitude – as often as 97 percent of the time.

Researchers claimed the software will help to improve the vertical accuracy of measurements in potentially hazardous regions at high altitudes, such as areas of soft, loose land that may be prone to landslides. They also claim that their software could be used to measure how quickly glaciers at high altitudes are melting.

GPS satellites transmit information in the form of radio waves to the GPS receiver held by the user. At the same time, the signals must also travel to at least one other ground-based receiver to obtain a location reference, which allows the user’s receiver in turn to accurately calculate its own position in 3D. Before the satellite signals reach the receivers, they must travel through Earth’s atmosphere, which results in time delays that affect accuracy.

When the user’s receiver and the reference receiver reside at drastically different altitudes, however, each location experiences different amounts of time delay, which complicates matters even further. So, in mountainous regions where height differences can vary greatly over a short distance, acquiring the altitude of locations to within a few centimetres is difficult.

“Time is the heart that drives GPS, so it is important that we have a proficient method that accounts for delays from earth’s atmospheric layers,” said Grejner-Brzezinska, one of the researchers. “It would be ideal for all GPS signals to travel in a straight line directly to their destination, but due to electron interaction and refraction in the lower atmosphere, the signal’s path is far from straight,” she continued.

Electron interaction and tropospheric refraction effectively re-route the GPS signal, which means that the signal travels an extra distance and requires extra time, said Grejner-Brzezinska.

She and her colleagues looked specifically at troposphere delays – those caused by the lowest level of the atmosphere. Their study can be found in a recent issue of the journal Measurement Science and Technology.

This research was funded by the European Space Agency Plan for European Cooperating States project and a grant from the Polish Ministry of Science and Higher Education.

Source: Ohio State University